1. Field of the Invention
The present invention relates to a physical quantity control device including first and second control means having different sensitivities and capable of changing at least one physical quantity according to first and second operational quantities to be individually input to said first and second control means, respectively, and first and second computing means for computing said first and second operational quantities according to a deviation between a predetermined target value and said physical quantity, wherein said physical quantity is feedback-controlled to be converged to said predetermined target value.
Further, the present invention also relates to a vehicle motion control device including operating means for outputting a physical quantity which effects a vehicle motion, first and second control means having different sensitivities and capable of changing said physical quantity output from said operating means according to first and second operational quantities to be individually input to said first and second control means, respectively, and first and second computing means for computing said first and second operational quantities according to a deviation between a predetermined target value and said output physical quantity, wherein said output physical quantity is feedback-controlled to converge to said predetermined target value.
2. Related Art
Conventionally, a known traction control device for a vehicle is so designed as to control a driving wheel speed as a physical quantity by controlling a throttle valve opening of an engine by a first control means and controlling a brake pressure by a second control means. Further, a known engine speed control device is so designed as to control a rotational speed of an engine mounted in a vehicle by controlling a throttle valve opening by a first control means, controlling a fuel supply quantity by a second control means, and controlling an ignition timing of the engine by a third control means.
However, in a case where the physical quantity is feedback-controlled to become the same target value by the two control means in two feedback control systems, interference is generated between both feedback control systems which will cause mutual disturbance because of a difference in response frequency (i.e., a difference in delay of control) between both feedback control systems.
To cope with this problem, it has been conventionally proposed that the feedback control is prevented from being conducted simultaneously in both feedback control systems by setting different target values or providing a time lag for the controls by both the feedback control systems (Japanese Patent Laid-open Publication Nos. 61-85249 and 58-16948, for example).
However, in the case of setting different target values as mentioned above, the two feedback control systems have the different target values for the same physical quantity, a weak control system of both the control systems is dragged to a strong control system by a difference between the target values. On the other hand, in the case of providing a time lag for the controls by both feedback control systems, the control is carried out by only one of the feedback control systems in a certain control time, with the result that a sufficient control performance cannot be exhibited in both the feedback control systems. Additionally, complex processing must be carried out when switching the control between both feedback control systems.
The present invention has been achieved in view of the foregoing, and it is an object of the present invention to provide a physical quantity control device which avoids the control interference between both control means and sufficiently exhibits the control performance of both the control systems. It is a further object of the present invention to provide a vehicle motion control device similar to said physical quantity control device.